1. Field of Invention
The present disclosure relates in general to a system for controlling operation of a subsea device. More specifically, the present disclosure relates to a pressure actuated sequencing valve assembly that selectively delivers fluid to a plug handling device.
2. Description of Prior Art
Subsea wells typically include a wellhead housing located on the sea floor; which are lined with one or more casing strings. Casing hangers are mounted in the wellhead housing for supporting the casing strings. In one type of wellhead assembly, a tubing hanger located at the upper end of a string of tubing is installed in the wellhead housing. After the tubing has been installed, the well can be perforated and a production tree landed on the wellhead housing. A plug is usually inserted into the production passage of the tubing hanger to temporarily seal the well when the production tree is being installed on the wellhead housing. Production trees have a number of valves for controlling the well fluid. Trees also have a production flow passage and an isolation sub that stabs into the production passage of the tubing hanger. The plug is generally removed by lowering a tool through the production flow passage of the tree. For a workover operation involving pulling of the tubing hanger, the tree must be disconnected from the wellhead housing. If the tree needed to be retrieved for repair work, this can be done without pulling the tubing.
In another type of wellhead assembly, the tree is installed on the wellhead housing before running the tubing. Here the drilling riser connects to the tree, and the tubing hanger is lowered through the drilling riser and lands in the tree. The tubing hanger has a lateral flow outlet that registers with a lateral flow outlet in the tree. In this type of wellhead assembly, the plug is set in the tubing hanger vertical bore above the flow outlet. The tree does not need to be disconnected from the wellhead housing for pulling the tubing for a workover operation. If the tree needed to be retrieved for repair, the tubing would have to be pulled.
In the various configurations described above, the tree is a large, heavy and complex assembly conventionally run on a string of drill pipe. The running procedure requires a vessel with a derrick. It may not be economical to utilize the same vessel that drilled the well to complete the well and install the tree. Designs for trees that can be run on a lift line are known.